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Diffstat (limited to 'rust/kernel/std_vendor.rs')
| -rw-r--r-- | rust/kernel/std_vendor.rs | 163 |
1 files changed, 163 insertions, 0 deletions
diff --git a/rust/kernel/std_vendor.rs b/rust/kernel/std_vendor.rs new file mode 100644 index 000000000000..b3e68b24a8c6 --- /dev/null +++ b/rust/kernel/std_vendor.rs @@ -0,0 +1,163 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +//! The contents of this file come from the Rust standard library, hosted in +//! the <https://github.com/rust-lang/rust> repository, licensed under +//! "Apache-2.0 OR MIT" and adapted for kernel use. For copyright details, +//! see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>. + +/// [`std::dbg`], but using [`pr_info`] instead of [`eprintln`]. +/// +/// Prints and returns the value of a given expression for quick and dirty +/// debugging. +/// +/// An example: +/// +/// ```rust +/// let a = 2; +/// # #[allow(clippy::dbg_macro)] +/// let b = dbg!(a * 2) + 1; +/// // ^-- prints: [src/main.rs:2] a * 2 = 4 +/// assert_eq!(b, 5); +/// ``` +/// +/// The macro works by using the `Debug` implementation of the type of +/// the given expression to print the value with [`printk`] along with the +/// source location of the macro invocation as well as the source code +/// of the expression. +/// +/// Invoking the macro on an expression moves and takes ownership of it +/// before returning the evaluated expression unchanged. If the type +/// of the expression does not implement `Copy` and you don't want +/// to give up ownership, you can instead borrow with `dbg!(&expr)` +/// for some expression `expr`. +/// +/// The `dbg!` macro works exactly the same in release builds. +/// This is useful when debugging issues that only occur in release +/// builds or when debugging in release mode is significantly faster. +/// +/// Note that the macro is intended as a temporary debugging tool to be +/// used during development. Therefore, avoid committing `dbg!` macro +/// invocations into the kernel tree. +/// +/// For debug output that is intended to be kept in the kernel tree, +/// use [`pr_debug`] and similar facilities instead. +/// +/// # Stability +/// +/// The exact output printed by this macro should not be relied upon +/// and is subject to future changes. +/// +/// # Further examples +/// +/// With a method call: +/// +/// ```rust +/// # #[allow(clippy::dbg_macro)] +/// fn foo(n: usize) { +/// if dbg!(n.checked_sub(4)).is_some() { +/// // ... +/// } +/// } +/// +/// foo(3) +/// ``` +/// +/// This prints to the kernel log: +/// +/// ```text,ignore +/// [src/main.rs:4] n.checked_sub(4) = None +/// ``` +/// +/// Naive factorial implementation: +/// +/// ```rust +/// # #[allow(clippy::dbg_macro)] +/// # { +/// fn factorial(n: u32) -> u32 { +/// if dbg!(n <= 1) { +/// dbg!(1) +/// } else { +/// dbg!(n * factorial(n - 1)) +/// } +/// } +/// +/// dbg!(factorial(4)); +/// # } +/// ``` +/// +/// This prints to the kernel log: +/// +/// ```text,ignore +/// [src/main.rs:3] n <= 1 = false +/// [src/main.rs:3] n <= 1 = false +/// [src/main.rs:3] n <= 1 = false +/// [src/main.rs:3] n <= 1 = true +/// [src/main.rs:4] 1 = 1 +/// [src/main.rs:5] n * factorial(n - 1) = 2 +/// [src/main.rs:5] n * factorial(n - 1) = 6 +/// [src/main.rs:5] n * factorial(n - 1) = 24 +/// [src/main.rs:11] factorial(4) = 24 +/// ``` +/// +/// The `dbg!(..)` macro moves the input: +/// +/// ```ignore +/// /// A wrapper around `usize` which importantly is not Copyable. +/// #[derive(Debug)] +/// struct NoCopy(usize); +/// +/// let a = NoCopy(42); +/// let _ = dbg!(a); // <-- `a` is moved here. +/// let _ = dbg!(a); // <-- `a` is moved again; error! +/// ``` +/// +/// You can also use `dbg!()` without a value to just print the +/// file and line whenever it's reached. +/// +/// Finally, if you want to `dbg!(..)` multiple values, it will treat them as +/// a tuple (and return it, too): +/// +/// ``` +/// # #[allow(clippy::dbg_macro)] +/// assert_eq!(dbg!(1usize, 2u32), (1, 2)); +/// ``` +/// +/// However, a single argument with a trailing comma will still not be treated +/// as a tuple, following the convention of ignoring trailing commas in macro +/// invocations. You can use a 1-tuple directly if you need one: +/// +/// ``` +/// # #[allow(clippy::dbg_macro)] +/// # { +/// assert_eq!(1, dbg!(1u32,)); // trailing comma ignored +/// assert_eq!((1,), dbg!((1u32,))); // 1-tuple +/// # } +/// ``` +/// +/// [`std::dbg`]: https://doc.rust-lang.org/std/macro.dbg.html +/// [`eprintln`]: https://doc.rust-lang.org/std/macro.eprintln.html +/// [`printk`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html +#[macro_export] +macro_rules! dbg { + // NOTE: We cannot use `concat!` to make a static string as a format argument + // of `pr_info!` because `file!` could contain a `{` or + // `$val` expression could be a block (`{ .. }`), in which case the `pr_info!` + // will be malformed. + () => { + $crate::pr_info!("[{}:{}]\n", ::core::file!(), ::core::line!()) + }; + ($val:expr $(,)?) => { + // Use of `match` here is intentional because it affects the lifetimes + // of temporaries - https://stackoverflow.com/a/48732525/1063961 + match $val { + tmp => { + $crate::pr_info!("[{}:{}] {} = {:#?}\n", + ::core::file!(), ::core::line!(), ::core::stringify!($val), &tmp); + tmp + } + } + }; + ($($val:expr),+ $(,)?) => { + ($($crate::dbg!($val)),+,) + }; +} |